A low-cost water quality monitoring prototype device with embedded chromogenic reagent capsules and dynamic colorimetric detection

A low-cost, compact, pumpless and valveless device is proposed in this study for water quality in field detection. Capsules filled with chromogenic reagent were fixed inside reservoirs. A series of reservoirs were mounted on a revolver. The device can automatically open the reservoirs and the capsule, so that the water sample can come inside then mix and react with the chromogenic reagent. During the reactions, the color data of samples were recorded dynamically and the chromogenic reaction rate constants were derived. According to different reaction rate constants, the concentration of target substance can be determined since the concentration and rate constant are positively correlated. A prototype was built and experiments were carried out to determine concentration of a typical nutrient, nitrite, in water samples to evaluate the effectiveness of the device. It was found that the limit of detection (LOD) for nitrite was approximately 0.01 mg/L. With minor modification, the device can be used to monitor quality parameters in natural water, and wastewater from sewage, agriculture, fishery or industry. (C) 2017 Published by Elsevier B.V.